Copper Lake

The LakeGrade rubric puts Copper Lake at a C: clarity at 7.0 ft, phosphorus readings still being added, and a TSI of 49 signal an intermediate trophic state. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

A TSI near 49 places Copper Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. The lake's 52 ft maximum depth is in the upper tier for Minnesota — deep enough for cold-water fish to find refuge in summer. The lake is compact at 37 acres, with 2.5 miles of shoreline and little volume to buffer nutrient inputs. Within Cook County's 128 graded lakes, Copper Lake ranks 78 — below the local median, though not at the bottom.

No invasive species are currently listed at Copper Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Copper Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. No formal public access is documented at Copper Lake — most use is by shoreline residents and their guests. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.